The European Championship was plunged into arguably its most serious racism row yet today after it emerged a banana may have been thrown at Mario Balotelli.
UEFA confirmed this afternoon they were "looking into" reports a photographer witnessed a steward retrieving a banana from the pitch during Italy's clash with Croatia yesterday.
The FARE (Football Against Racism in Europe) network also announced their observers heard between 300 and 500 Croatia fans chanting monkey noises at Balotelli in the 1-1 Group C draw in Poznan.
UEFA confirmed they were aware of the racism claims, telling Press Association Sport: "We are looking into the reports."
If yesterday's purported banana-throwing incident is shown to be intended as an insult towards Balotelli, the fallout would be potentially the biggest yet at a tournament that has been dogged by allegations of racist abuse.
Balotelli said before Euro 2012 that he would "kill" anyone who threw a banana at him in the street and threatened to walk off the pitch if racially abused.
UEFA are already probing allegations the Manchester City striker, 21, was subjected to monkey chants in Italy's opening match against Spain on Sunday.
That may have been missed by FARE observers but yesterday's apparent repeat was not.
European football's leading anti-racism campaigners posted on their Twitter feed: "FARE observers report between 300 and 500 supporters of Croatia involved in racially abusing Mario Balotelli at last nights match in Poznan.
"UEFA received the observers reports this afternoon. We are working with them to provide as much information as possible.
"We congratulate the Italian fans for their support of Balotelli last night. Many sang his name to drown out the monkey chants £no2racism."
Italy boss Cesare Prandelli, who on Monday rejected claims Balotelli was racially abused during the game against Spain, insisted today he was unaware of yesterday's alleged banana-throwing incident.
"No, I haven't seen anything," he said.
The Italian Football Federation (FIGC) later confirmed the claims and accompanying photograph had been brought to their attention but added that no-one from their delegation witnessed the incident during the game.
A spokesman told Press Association Sport: "There's not any official complaint at the moment about that.
"It's not quite clear where this photograph was shot at the game and whether it [the banana] was launched against Mario Balotelli."
As well as incidents surrounding Balotelli, UEFA are looking into allegations Czech Republic defender Theodor Gebre Selassie was subjected to monkey chants during his side's Group A opener against Russia last Friday.
Holland players claimed they heard racist chanting during an open training session in Krakow last Wednesday before the tournament even began.
The FIGC, meanwhile, have written to UEFA expressing "great regret" that their national anthem was booed by Spain and Croatia fans during their Euro 2012 Group C matches.
In a statement, the Italian federation confirmed vice-president Demetrio Albertini had sent a letter to UEFA general secretary Gianni Infantino to complain.
The FIGC acknowledged Italy supporters had jeered anthems in the past.
FARE also confirmed today that they had passed on to UEFA complaints over comments made by Italy striker Antonio Cassano about homosexuals this week.
Cassano later apologised after saying he hoped there were no "queers" among his team-mates.
The Croatian Football Federation (HNS) were hit with a 25,000-euro (£20,298) fine this afternoon for the setting-off and throwing of fireworks and missiles, and a pitch invasion by a supporter, during Sunday's win over Ireland.
The HNS could face further action following a repeat against Italy last night, while any conviction for racist abuse may lead to even more severe sanctions.